Early changes occuring in the lens during cataract formation include increased intracellular Na+ and Ca++ and decreased K+, and osmotic swelling followed by alterations in lens protein biosynthesis, aggregation of lens proteins, and opacification. In addition, lens membrane proteins undergo proteolysis, oxidation and aggregation during cataract formation. The goal of this project is to determine whether or not there are structural changes in lens NaK-ATPase that could account for the changes in intracellular electrolytes that may lead to cataract formation. NaK-ATPase (the sodium pump) is an ubiquitous plasma membrane bound oligomer (yield catalytic subunit and B glycoprotein subunit) with Na+ and K+ activated ATPase activity. The pump functions in the transmembrane pumping of ions, maintenance of ion gradients and cell volume regulation. The specific aims of this proposal include the immunodetection and characterization (by molecular weights) of normal lens NaK-ATPase subunits followed by the immunodetection of NaK-ATPase subunits in cataracts to determine whether aggregation or proteolysis has occurred. The immunodetection method includes resolving membrane proteins by SDS-PAGE, coupling them to diazotized paper incubating with antisera to NaK-ATPase, and detecting NaK-ATPase subunits by autoradiography. This study should provide the preliminary data necessary to propose a more extensive study of age dependent structural changes in lens NaK-ATPase and their relationship to cataractogenesis.